The present invention relates to the shape of an airway adaptor for, in carbon dioxide measurement for detecting and measuring the existence, concentration, and the like of carbon dioxide in the respiratory gas expired through the nostrils or mouth of the living body, guiding the expired gas discharged through the nostrils or mouth of the living body, thereby allowing a measurement relating to carbon dioxide in the expired gas to be effectively performed. The airway adaptor is configured so that, in the case where a carbon dioxide sensor is to be attached to the airway adaptor, the operations of attaching or detaching the sensor can be performed simply and easily.
For example, a related-art carbon dioxide sensor for detecting and measuring the existence, concentration, and the like of carbon dioxide in the expired gas discharged through the nostrils or mouth of the living body is configured in the following manner (see JP-A-2003-315264). An airway case is provided in which transmissive windows through which light is transmitted are disposed on right and left side faces of an airtight case that is formed in a cylindrical or box-like shape, respectively, and openings for guidingly introducing the expired gas and leading the gas to the outside are formed in the upper and lower faces or the like, respectively. On the side faces of the airway case in which the transmissive windows are disposed, a light emitting element and a light receiving element are supported by supporting members, respectively while being opposed to each other. Light which is transmitted through the expired gas passing through the interior of the airway adaptor is detected and measured.
In order to effectively introduce the expired gas discharged through the nostrils of the living body into the airway case for attaching the carbon dioxide sensor, the airway adaptor is configured so that one side has nasal tubes which are to be inserted respectively into the two nostrils of the living body, and the other side is connected to a hole portion disposed in the airway case. The carbon dioxide sensor is configured so as to be detachable from the airway case.
In the thus configured carbon dioxide sensor, the measurement object is the expired gas discharged through the nostrils of the living body, and therefore the nasal tubes are attached to the nostrils with using an airway adaptor. Accordingly, the sensor can be applied also to a mask which is configured as a mask for carbon dioxide measurement having a nasal mask shell.
From this viewpoint, a related-art carbon dioxide nasal mask has been developed, which, even when a gas is supplied at a high flow rate from the outside into the mask, can correctly measure the concentration of carbon dioxide, and which is configured so that oxygen or the like can be forcibly supplied (see JP-A-2008-200061).
Namely, the carbon dioxide nasal mask disclosed in JP-A-2008-200061 includes: a nasal mask shell which has a close contact edge adapted to be brought into close contact with the face so as to cover the nose, and the interior of which configures a sealed space; an airway case which is formed in a part of the nasal mask shell, which, in a state where the nasal mask shell is worn, is positioned immediately below the nostrils, thereby allowing the expired gas expired through the nostrils to be introduced, which has an expired gas discharge port for discharging the introduced expired gas, and which is used for detachably attaching a carbon dioxide sensor to the outside of the nasal mask shell; an introduction port for allowing a gas such as oxygen or air to be introduced from the outside into the nasal mask shell; and a nasal tube for ensuring a passage through which, in the nasal mask shell, the expired gas that is introduced from the nostrils into the airway case is guided to the airway case without being diluted by the gas arriving from the introduction port.
In the thus configured carbon dioxide nasal mask, the expired gas reaches the airway case through the nasal tube, and adequately escapes into the nasal mask shell through the expired gas discharge port. Even when oxygen or the like arrives at the introduction port disposed in the nasal mask shell, therefore, accurate carbon dioxide measurement is enabled without causing the expired gas from the nose to be diluted by oxygen or the like which flows into from the introduction port. Since the nasal mask shell is in close contact with the face in the close contact edge, the oxygen or the like arriving at the introduction port can be used for generating a positive pressure, and hence can be used in an apparatus for CPAP (Continuous Positive Airway Pressure) or NPPV (Noninvasive Positive Pressure Ventilation) therapy which is used in treatment of a patient suffering from sleep apnea syndrome or respiratory failure. Therefore, carbon dioxide measurement under positive pressure ventilation which is hardly performed in the prior art is enabled.
In JP-A-2008-200061, the airway case which is disposed in the carbon dioxide nasal mask, and which is used for attaching the carbon dioxide sensor is formed as a part of the nasal mask, the Y-shaped nasal tube which can be inserted into the nostrils is disposed in one end of the airway case, and the other end is disposed so as to be opposed to an open port disposed in the airway case. With respect to the thus configured airway case, it is necessary to obtain a configuration arrangement where the inlet and outlet for the expired gas are disposed so as to be opposed to each other, and, in order to allow the introducing flow of the expired gas to easily move, the whole airway case is housed inside the carbon dioxide nasal mask.
As described above, the carbon dioxide nasal mask has a complex design, and hence works such as assembling of a plurality of parts and maintenance are required. When the mask and the airway case are made detachable without causing air leakage, there arises a problem in that the structure is complicated. Also in the case where the carbon dioxide sensor is attached to the airway case, the sensor must be incorporated inside the nasal mask, and there is a disadvantage in that the attaching and detaching operations are cumbersome.
Moreover, the carbon dioxide nasal mask has a special shape which is complexly designed, and hence is difficult to be produced. Therefore, problems in production technique and cost remain to be solved.